Seasonal changes in metal and nutrient fluxes across the sediment-water interface in tropical mangrove creeks in the Amazon region

Matos, Christiene R.L.; Berrêdo, José Francisco; Machado, Wilson; Metzger, Édouard; Sanders, Christian J.; Faial, K.C.F.; Cohen, Marcelo Cancela Lisboa

doi:10.1016/j.apgeochem.2022.105217

Cited by 14 publications

(4 citation statements)

References 80 publications

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“…Although limited, existing studies on the sulfidation of pure Fh ,, and influence of coprecipitated OM on Fe(II)-catalyzed Fh transformation , suggest that the anoxic reductive dissolution of ferrihydrite and its pyritization under OM loading depend on various factors, including OM properties, C/Fe ratio, S(-II)/Fe ratio, and pH. , Yet, few studies have systematically evaluated the impact of the abovementioned factors as well as their interactions on the sulfidation of Fh–OM coprecipitates. In porewaters of OM-rich wetland and estuarine sediments, both C/Fe molar ratios (0.2–25.0) , and DS(-II) concentrations (0.023–5.0 mM) − have wide spectrum. Considering the controlling effect of the S(-II)/Fe molar ratio in pure Fh sulfidation, , we therefore hypothesize that the kinetics and mineralogical evolution pathways of Fh–OM sulfidation depend on the interrelated effects of carbon and sulfur loadings.…”

Section: Introductionmentioning

confidence: 99%

Transformations of Ferrihydrite–Extracellular Polymeric Substance Coprecipitates Driven by Dissolved Sulfide: Interrelated Effects of Carbon and Sulfur Loadings

Wang

et al. 2023

Environ. Sci. Technol.

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The association of poorly crystalline iron (hydr)oxides with organic matter (OM), such as extracellular polymeric substances (EPS), exerts a profound effect on Fe and C cycles in soils and sediments, and their behaviors under sulfate-reducing conditions involve complicated mineralogical transformations. However, how different loadings and types of EPS and water chemistry conditions affect the sulfidation still lacks quantitative and systematic investigation. We here synthesized a set of ferrihydrite−organic matter (Fh−OM) coprecipitates with various model compounds for plant and microbial exopolysaccharides (polygalacturonic acids, alginic acid, and xanthan gum) and bacteriogenic EPS (extracted from Bacillus subtilis). Combining wet chemical analysis, X-ray diffraction, and X-ray absorption spectroscopic techniques, we systematically studied the impacts of C and S loadings by tracing the temporal evolution of Fe mineralogy and speciation in aqueous and solid phases. Our results showed that the effect of added OM on sulfidation of Fh−OM coprecipitates is interrelated with the amount of loaded sulfide. Under low sulfide loadings (S(-II)/Fe < 0.5), transformation to goethite and lepidocrocite was the main pathway of ferrihydrite sulfidation, which occurs more strongly at pH 6 compared to that at pH 7.5, and it was promoted and inhibited at low and high C/Fe ratios, respectively. While under high sulfide loadings (S(-II)/Fe > 0.5), the formation of secondary Fe−S minerals such as mackinawite and pyrite dominated ferrihydrite sulfidation, and it was inhibited with increasing C/Fe ratios. Furthermore, all three synthetic EPS proxies unanimously inhibited mineral transformation, while the microbiogenic EPS has a more potent inhibitory effect than synthetic EPS proxies compared at equivalent C/Fe loadings. Collectively, our results suggest that the quantity and chemical characteristics of the associated OM have a strong and nonlinear influence on the extent and pathways of mineralogical transformations of Fh−OM sulfidation.

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Section: Introductionmentioning

confidence: 99%

Transformations of Ferrihydrite–Extracellular Polymeric Substance Coprecipitates Driven by Dissolved Sulfide: Interrelated Effects of Carbon and Sulfur Loadings

Wang

et al. 2023

Environ. Sci. Technol.

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“…Dissolved [Nd] and [Hf] of the Pará River endmember (Sal = 0.3) are 1036 pmol kg -1 and 13.4 pmol kg -1 , respectively, and are thus significantly higher than 502 pmol kg -1 and 12.3 pmol kg -1 of the Amazon River freshwater endmember (Sal = 0.2) (Supplementary Data 1 ). These higher concentrations are likely a result of the overall lower pH of the Pará River pH of 6.2–7.4 (Amazon River: 6.8–7.3) 27 and/or feeding by tributaries from the mangrove forests, which is consistent with high trace metal export from the Amazonian mangrove forest areas 28 – 30 . In addition, parent rock characteristics and floodplain supply may play a role given that elevated REY concentrations in the waters exiting the floodplain have been observed in the Amazon Basin 31 .…”

Section: Resultsmentioning

confidence: 56%

Overlooked riverine contributions of dissolved neodymium and hafnium to the Amazon estuary and oceans

Hathorne

Laukert

2023

Nat Commun

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The Amazon River accounts for 20% of global freshwater runoff and supplies vital trace metals to the Atlantic Ocean. Suspended particles within its plume are thought to partially dissolve, constituting a large potential source of metals, which is, however, not well constrained. Here we used combined neodymium (Nd) and hafnium (Hf) isotopes to disprove the release of Nd and Hf from particles as the cause of the observed dissolved concentration increases and isotopic variability across the plume. Instead, the changes reflect admixture of nearby Pará River freshwater with exceptionally high dissolved Nd and Hf concentrations contributing 45–100% of the riverine fraction to the southern and outer estuary. This result led us to develop an empirical relationship between riverine Nd concentration and pH to revise the global dissolved riverine Nd flux, which accordingly is at least three times higher than commonly used estimates. Future work should focus on contributions of low-pH rivers to global metal fluxes.

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“…Further, the seasonal shift affects the vertical redoxcline within the sediment and the fluxes of substances across the sedimentwater interface. In the wet season, under suboxic conditions, fluxes of Fe 2+ , Mn 2+ , NH 4+ , and PO 3 4 to the water column increases, to a point to surpass burial rates of Mn, for example, but not of Fe and nutrients (Matos et al, 2022). These observations support the role of mangrove-fringed tidal creeks, harboring intense biogeochemical processes, rather than simple exchange of dissolved materials with adjacent waters, these mechanisms are strongly influenced by rainfall intensity and distribution pattern which are strongly affected by climate change.…”

Section: Rainfall Reductionmentioning

confidence: 99%

Mangrove Trace Metal Biogeochemistry Response to Global Climate Change

Lacerda¹,

Ward²,

Borges³

et al. 2022

Front. For. Glob. Change

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This review discusses observed impacts from different climate change-driven pressures on mangrove's role in modulating trace metal transfer at the land-ocean interface. It contributes to the literature in a global context and shows mangroves as mitigators or providing positive feedback to metal mobilization. Most chalcophile metals2+ accumulate in mangrove soils associated with sulfides while high sedimentation rates avoid their oxidation. Exudation of oxygen by roots fixates Fe, which co-precipitates metals as oxyhydroxides in the rhizosphere. These two biogeochemical processes reduce trace metal availability to plants and their mobility within estuaries. However, climate change-driven pressures alter this geochemical equilibrium. Increasing atmospheric CO2 and temperature, and the intensity and frequency of extreme climatic events, have proved to affect mangrove functioning and cover, but no direct observation on the impact on metal biogeochemistry is presently available, whereas sea level rise and saline intrusion impacts on the fate of metals have already been observed. Sea level rise increases erosion, that dissociates deposited sulfides releasing metals to the water column. Released metals adsorb onto suspended particles and can re-deposit in the estuary or are exported to continental shelf sediments. Saline intrusion may oxidize deeper sediment layers releasing metals to porewaters. Part of the mobilized metals may remain in solution complexed with DOM and have their bioavailability increased, as shown by high bioaccumulation factors and biomagnification and high metal concentrations in the estuarine biota, which results in higher human exposure through fisheries consumption. Since erosion occurs preferentially at the sea border and higher sedimentation at the higher reaches of the estuary, triggering mangroves migration landward, spatial gradients are formed, and shall be taken into consideration when planning mitigation or adaptation strategies. These observations suggest disruption of traditional humans dwelling in mangrove dominated coastlines by increasing contamination of coastal fisheries, often the principal protein source for those groups and an important source of income. Further research into the environmental and socioeconomic impacts of climate change driven alterations to metal biogeochemical processes in mangroves as contaminant levels are expected to increase.

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Seasonal changes in metal and nutrient fluxes across the sediment-water interface in tropical mangrove creeks in the Amazon region

Cited by 14 publications

References 80 publications

Transformations of Ferrihydrite–Extracellular Polymeric Substance Coprecipitates Driven by Dissolved Sulfide: Interrelated Effects of Carbon and Sulfur Loadings

Transformations of Ferrihydrite–Extracellular Polymeric Substance Coprecipitates Driven by Dissolved Sulfide: Interrelated Effects of Carbon and Sulfur Loadings

Overlooked riverine contributions of dissolved neodymium and hafnium to the Amazon estuary and oceans

Mangrove Trace Metal Biogeochemistry Response to Global Climate Change

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